The present invention relates to a plasma thin-film deposition method for depositing a fluorine containing carbon film, which can be used as, e.g., an interlayer dielectric film of a semiconductor device, by a plasma treatment.
In order to achieve the high integration of a semiconductor device, it has been developed to provide devices, such as the scale down of a pattern and the multilayering of a circuit. As one of such devices, there is a technique for multilayering wirings. In order to provide a multilevel interconnection structure, a number n wiring layer and a number (n+1) wiring layer are connected to each other by means of a conductive layer, and a thin-film called an interlayer dielectric film is formed in a region other than the conductive layer.
A typical interlayer dielectric film is an SiO2 film. In recent years, in order to more accelerate the operation of a device, it has been required to reduce the relative dielectric constant of the interlayer dielectric film, and the material of the interlayer dielectric film has been studied. That is, the relative dielectric constant of an SiO2 film is about 4, and it has been diligently studied to dig up materials having a smaller relative dielectric constant than that of the SiO2 film. As one of such materials, it has been studied to put an SiOF film having a relative dielectric constant of 3.5 to practical use. The inventor has taken notice of a fluorine containing carbon film (which will be hereinafter referred to as a xe2x80x9cCF filmxe2x80x9d) having a still smaller relative dielectric constant. The CF film is deposited by means of, e.g., the thermal CVD (Chemical Vapor Deposition) or the plasma CVD.
Therefore, the inventor has intended to produce a CF film having high adhesion and hardness using a plasma system for producing a plasma by the electron cyclotron resonance, using gases containing, e.g., a compound gas of carbon (C) and fluorine (F) and a hydrocarbon gas, as thin-film deposition gases, on various process conditions.
However, the CF film has the following problems. FIG. 6 shows a part of a circuit part formed on a wafer, wherein reference numbers 11 and 12 denote CF films, 13 and 14 denoting conductive layers of W (tungsten), 15 denoting a conductive layer of Al (aluminum), 16 denoting an SiO2 film, into which P and B have been doped, and 17 denoting an n-type semiconductor region. The W layer 13 is formed at a process temperature of 400 to 450xc2x0 C. At this time, the CF films 11 and 12 are heated to the process temperature. However, if the CF films are heated to such a high temperature, a part of Cxe2x80x94F bonds are cut, so that F contag gases are mainly desorbed. The F containing gasses include F, CF, CF2 gases and so forth.
If the F containing gases are thus desorbed, there are the following problems.
(a) The metal wirings of aluminum, tungsten and so forth are corroded.
(b) Although the insulator film also has the function of pressing the aluminum wiring to prevent the swell of aluminum, the pressing force of the insulator film on the aluminum wiring is decreased by degassing. As a result, the aluminum wiring swells, so that an electrical defect called electromigration is easily caused.
(c) The insulator film cracks, so that the insulation performance between the wirings gets worse. When the extent of the crack increases, it is not possible to form a wiring layer at the next stage.
(d) if the amount of desorbed F increases, the relative dielectric constant increases.
It is therefore an object of the present invention to eliminate the aforementioned problems and to provide a plasma thin-film deposition method capable of depositing an insulator film of a CF film, which has strong bonds and high thermostability, e.g., an interlayer dielectric film of a semiconductor device.
According to one aspect of the present invention, according to a first aspect of the present invention, a plasma thin-film deposition method comprises the steps of: activating a thin-film deposition gas containing a compound gas of carbon and fluorine and an oxygen containing gas to form a plasma; and depositing a fluorine containing carbon film on a substrate to be treated, with the plasma.
The oxygen containing gas may be carbon monoxide gas. Alternatively, the oxygen containing gas may be carbon dioxide gas. The oxygen containing gas may also be oxygen gas. In addition, the oxygen containing gas may be water gas. Moreover, the oxygen containing gas may be hydrogen peroxide gas. The thin-film deposition gas may include a hydrocarbon gas. In addition, the thin-film deposition gas may be activated by the interaction between a microwave and a magnetic field to form a plasma.
According to a second aspect of the present invention, a plasma thin-film deposition method comprises the steps of: activating a thin-film deposition gas containing a compound gas of carbon and fluorine and a silicon containing gas to form a plasma; and depositing a fluorine containing carbon film on a substrate to be treated, with the plasma. The silicon containing gas may be a compound gas of silicon and hydrogen. Alternatively, the silicon containing gas may be a compound gas of silicon and fluorine.
According to the second aspect of the present invention, a plasma thin-film deposition method comprises the steps of: activating a thin-film deposition gas containing a compound gas of carbon and fluorine, a hydrocarbon gas and silicon gas to form a plasma; and depositing a fluorine containing carbon film on a substrate to be treated, with the plasma. The thin-film deposition gas may include a hydrocarbon gas. The silicon containing gas may be a compound gas of silicon and hydrogen. Alternatively, the silicon containing gas may be a compound gas of silicon and fluorine.
According to a third aspect of the present invention, a plasma thin-film deposition method comprises the steps of: activating a thin-film deposition gas containing C4F8 gas and acetylene gas to form a plasma; and depositing a fluorine containing carbon film on a substrate to be treated, with the plasma. The flow ratio of C4F8 gas to acetylene gas may be 4/7xe2x89xa6C4F8 gas/acetylene gasxe2x89xa61.
According to a fourth aspect of the present invention, a plasma thin-film deposition method comprises the steps of: activating a thin-film deposition gas containing C4F8 gas, acetylene gas and hydrogen gas to form a plasma; and depositing a fluorine containing carbon film on a substrate to be treated, with the plasma, wherein the flow ratio of C4F8 gas to acetylene gas is 0.7xe2x89xa6C4F8 gas/acetylene gasxe2x89xa64/3, and the flow ratio of the mixed gas of C4F8 gas and acetylene gas to hydrogen gas is 1xe2x89xa6the mixed gas/hydrogen gasxe2x89xa63.
According to the first through fourth aspects of the present invention, it is possible to produce a CF film which has high thermostability and small desorption of F containing gases. Therefore, if this CF film is used as, e.g., an interlayer dielectric film of a semiconductor device, it is possible to prevent the corrosion of a metal wiring, the swell of an aluminum wiring and the crack of the film. Since the scale down and accelerating of semiconductor devices have been required and since CF films have been widely noticed as insulator films having a small relative dielectric constant, the present invention is effective in the practical use of CF films as insulator films.